1. Field of the Invention
The invention relates to a cooling capsule (heat sink) for a thyristor, and in particular, to a cooling capsule which includes at least one heat transfer surface for providing a heat-conducting connection to the thyristor, and a metallic core through which extends a flow path for carrying a cooling medium from an inlet opening to an outlet opening.
2. Description of the Product
Cooling capsules of the above type, which are used particularly for cooling disk-type thyristors, as disclosed in German Offenlegungsschrift No. 2,116,302. A typical cooling capsule is formed from a cylindrical core having opposing end faces. The inlet and the outlet openings of the capsule are situated in the end faces and the flow path is comprised of a plurality of holes or bores extending therebetween and opening into the inlet and outlet openings. The capsule is further provided with covers, each for covering one end face of the core. The surfaces of the covers facing away from the core form heat transfer surfaces for the connection to a thyristor, while the surfaces facing toward the core are provided with circular concentric slots for connecting the bores running through the core. The covers are held to the core in a liquid-tight manner by rivet connections.
The above-described cooling capsules are used for cooling individual disk-type thyristors which are clamped between two cooling capsules, or they are used in so-called thyristor columns for cooling several disk-type thyristors. In the latter case, the disk-type thyristors of the column are stacked next to each other and on each side of a disk-type thyristor, a capsule is inserted and rests with its heat transfer surface against the disk-type thyristor. Thyristor columns of the aforesaid type are disclosed, for example, in the German Offenlegungsschrift No. 1,914,790.
The components of the above-described cooling capsule can all be fabricated on a screw machine and the only further processing required is drilling of some of the components on a drill press. In spite of this far-reaching automation, the manufacture of the cooling capsules is relatively expensive. Difficulties are encountered in the fabrication of the heat transfer surfaces of the covers, which are required to be flat and plane-parallel. In general, it is necessary to subject the already riveted cooling capsule to a grinding operation to obtain suitable heat transfer surfaces. This adds a further operation to the fabrication process resulting in additional labor and machine costs.
In an attempt to avoid the above problems, a cooling capsule for a thyristor has been proposed wherein the capsule comprises a cylindrical core of heat conductive material, the latter core being provided with flow paths arranged in planes which are approximately parallel to an end face of the core forming a heat transfer surface. The flow paths are in the form of straight bores which run between two recesses disposed in opposing outer surfaces of the core and into which respective inlet and outlet openings open. The core is surrounded by a hollow, cylindrical shaped member through which extend the inlet and outlet openings. This member provides a covering for the recesses and is connected to the core in a coolant-tight manner.
In the above cooling capsule, each bore may extend along a straight path from one recess to the other. However, in the gap between the core and the hollow cylindrical member, corrosion, so-called "crevice corrosion," can occur, as it is difficult to seal this gap against entering liquid coolant.
It is an object of the present invention to provide a cooling capsule of the above type which can be easily manufactured using mass production techniques.